The field of this invention is, in general, radar circuitry, and more particularly novel circuitry for processing Doppler signals received by radar sets. The circuits of the present invention permits a maximum of information to be obtained from Doppler-shifted echo signals, permits Doppler signals related to incoming and outgoing targets to be preserved and displayed, and it provides a Doppler signal discriminator including a voltage-controlled oscillator which is part of a feedback loop. The feedback feature permits the circuit to continually track a Doppler signal which may be rapidly changing its frequency. The circuits utilize novel dual channel frequency measuring circuitry as part of the feedback type discriminator. Circuits are shown for processing different types of Doppler signals characteristic of different types of radar sets.